Visit https://airtable.com/api and select a base. Then open your browsers console (Developer Tools) and run the following https://community.airtable.com/t/metadata-api-for-schema-and-mutating-tables/1856/6

Airtable metadata.js

var myapp = {
	id:window.application.id,
	name:window.application.name,
	tables:[]
};

for (let table of window.application.tables){

	var mytable = {
			id:table.id,
			isEmpty:table.isEmpty,
			name:table.name,
			nameForUrl:table.nameForUrl,
			primaryColumnName:table.primaryColumnName,
			columns:[]
	};

	for (let column of table.columns){
		var mycolumn = {
			id:column.id,
			name:column.name,
			type:column.type,
			typeOptions:column.typeOptions
		};

		mytable.columns.push(mycolumn);

	}

	myapp.tables.push(mytable);

}

jQuery('link[rel=stylesheet]').remove();
jQuery("body").html(JSON.stringify(myapp));
console.log(myapp);